This invention relates to a particle separator for separating particles from a stream of gas, and in particular to a particle separator using mini-cyclones that separate the particles from the gas stream and concentrate those particles within a quantity of liquid to be collected and monitored.
The collection and monitoring of particles separated from a gas is needed in many diverse situations. Some of these situations include defense against biological warfare agents in battlefield and other military applications; and protecting the general public against: airborne pathogenic agents released by terrorist groups; genetically modified material used in biotechnology applications; infectious organisms contaminating air in hospitals, research labs, public buildings, and confined spaces such as subway systems; and pollutant aerosols that damage the respiratory system.
Bioaerosols are defined as airborne particles, large molecules or volatile compounds that are living, contain living organisms or were released from living organisms. The size of a bioaerosol particle may vary from 100 microns to 0.01 micron.
There is an increasing concern about the presence of aerosolized biocontaminants associated with the food processing industry. E. coli, salmonella, xe2x80x9cMad Cowxe2x80x9d disease and other contaminants have resulted in widespread public concern about the safety of food products. The collection and measurement of bioaerosols are of interest to a wide community of public health officials because they can cause infectious diseases or chemical damage to the respiratory system. These particles are also of concern to the Department of Defense (DOD) because of their possible use in biological warfare and terrorism.
Air quality monitoring is also an important public health need. As the world""s population rises exponentially and world travel becomes increasingly easy, the degree and pace at which communicable diseases can spread has resulted in significant concerns regarding potential epidemics from airborne disease transmission. Recirculation of air in buildings and other enclosed spaces such as subways and airplanes has lead to a potentially significant public health issue. Identification and control of infectious disease organisms in hospitals represents another major need. The Environmental Protection Agency cites indoor air pollution causing xe2x80x9csick building syndromexe2x80x9d as one of the five major environmental problems in the United States (Federal Register, Apr. 5, 1994; the regulatory driver for the quality of indoor air as proposed regulations for OSHA). According to the EPA, indoor air pollution affects 33 to 55 percent of commercial buildings, and causes 13.5 million lost work days each year. It can also lead to major public health incidents.
Nosocomial, or hospital-acquired, infections are often caused by antibiotic resistant microorganisms. These infections currently affect around 10% of hospital patients, causing additional suffering and mortality. The detection of pathogenic materials such as nosocomial pneumonia and Legionnaires disease in ventilation systems could help prevent infectious outbreaks of unknown origin in hospitals and public buildings. A miniaturized collection/detection system could easily be placed within the ventilation ducts of buildings and left sampling for an extended length of time.
The use of recombinant microorganisms is an expanding area of biotechnology for production of biochemicals, pharmaceuticals and vaccines. Increasingly, recombinant viral vectors are being used for vaccine delivery and gene therapy. Effective containment measurements are required but there is a need to be able to measure the effectiveness of these containment measures. For example, there is the possibility that aerosols created accidentally by laboratory procedures may escape from the containment provided by microbiological safety cabinets. Or, aerosols may be created by centrifugation, or liquid handling. At present, the means by which airborne viruses and bacteria can be detected and monitored are limited.
Threats from microorganisms in the air as a result of natural phenomena or human-induced activities such as the examples discussed above cannot be adequately monitored and evaluated with current technology. Early warning, hazard recognition, personal protective equipment, exposure evaluation, and environmental monitoring are needed to prevent and reduce impacts from airborne infectious or genetically modified material. Near real-time monitoring is necessary to avoid exposure and to initiate early treatment to arrest disease progression. Existing collection devices such as filters do not provide real time information because they must be taken to a laboratory for analysis. Detection devices for real time use by the military currently are large and power intensive.
A further deficiency with large collectors is that they have high inlet velocities and can severely damage or kill the microorganisms being collected. A high flow rate system that uses one large cyclone chambers requires a high inlet gas velocity for proper efficiency. However, a high inlet gas velocity also creates a large pressure drop across the cyclone chambers that results in a high power consumption. Further, microorganisms usually have to be collected alive for effective detection. The high inlet velocity needed for efficiency places large shear forces against the particles, killing the microorganisms needed alive for analysis.
Therefore, there is a need for small, efficient gas (aerosol) collectors to separate, capture and concentrate bioparticles from the air for detection.
The particle separation and collection assembly of the present invention uses cyclonic forces to separate and remove small particles from an airstream and concentrate small particles for sensor/detector technology. This system utilizes multiple mini-cyclones operating in parallel to reduce the velocity of the intake air while maintaining the same fluid or flow rate as compared to one large cyclone.
In one embodiment of the present invention, the particle separator and collection assembly comprises a plurality of particle separation chambers; each of the particle separation chambers having a conical shape with an internal surface; a lower vacuum chambers disposed in fluid communication with the particle separation chambers; a plurality of inlets, each inlet disposed in fluid communication with each particle separation chambers, each inlet supplying particle-laden gas external from the assembly to each particle separation chambers; and a liquid passage conduit connectable to a reservoir; the liquid passage conduit supplying a liquid from a reservoir to the internal surface of each particle separation chambers in order to collect the particles separated from the gas within each particle separation chambers.
In an alternate embodiment of the present invention, the particle separator and collection assembly includes a two stage system of concentric components to remove large interfering particles and retain small particles for collection and analysis. In this assembly, a large outer cyclone is used to separate particles  greater than 50xcexc and an inner bank of mini-cyclones is used to capture and concentrate small particles  less than 50xcexc. The two stage particle separator and concentrator assembly comprises a housing having a longitudinal axis, the housing including a top end portion connectable to a blower and a bottom end connectable to a pump; at least one cyclone chambers disposed within the housing and having an upper end and a lower end; and at least one housing inlet in fluid communication with at least one cyclone chamber, at least one housing inlet enabling particle-laden gas external from the apparatus to enter the at least one particle separation chambers; a liquid passage conduit disposed within the housing and connectable to a pump, the liquid passage conduit delivering the liquid to the upper end of the least one cyclone chambers; and an outer cyclone chambers concentric to the longitudinal axis and coupled to the housing, the outer cyclone chambers in fluid communication with the inlet, wherein particle-laden gas is pulled through the at least one cyclone chambers by a blower so that the particles are separated from the gas by centrifugal force and collected by the liquid supplied to the at least one cyclone chambers.
The present invention further includes a method for separating particles from a gas and collecting the particles within a liquid using a particle separation assembly, the particle separation assembly having a plurality of cyclone separation chambers disposed longitudinally within a housing of the assembly and having a longitudinal axis, the housing including a top end connectable to a blower, a bottom end connectable to a pump, and a plurality of inlets corresponding to the plurality of cyclone separation chambers for external gas to enter the assembly, a liquid passage conduit connectable to the pump for delivering the liquid to each cyclone separation chambers, the method comprising: drawing a particle-laden gas into the inlets of the housing and through the plurality of cyclone separation chambers so that a centrifugal force is created due to the configuration of the chambers; separating the particles from the gas by using the centrifugal force to move the particles outwardly away from the longitudinal axis and toward the inner wall of each cyclone chambers; supplying each cyclone chambers with the liquid through the liquid passage conduit; collecting the particles with the liquid by washing down the inner wall of each cyclone chambers and trapping the particles within the liquid.
The microassembly approach to aerosol collection of the present invention is advantageous by allowing process routes through large surface to volume ratios and short response times. Parallel processing using micro components allows process optimization of a single unit and subsequent scale-up by replication. Miniaturization of components also allows multi-component processing of an airstream for more efficient particle collection and concentration.
It is advantageous using a bank of miniature cyclones (1-3 cm diameter) in parallel. Parallel processing using multiple mini-cyclone chambers reduces the pressure drop across the separation unit significantly while processing the same amount of fluid (same fluid or flow rate) with the same efficiency as one large cyclone chambers. This also provides an assembly that has low power consumption due to lower inlet air velocity. Further, the lower inlet air velocity reduces the shear forces and abrasive wear against the particles and the continuous underfluid or flow commonly associated with the cyclone.
Another advantage of an assembly consisting of multiple mini-cyclones is that of total assembly size and volume. In terms of internal volume, our calculations indicate that a mini-cyclone assembly can be almost an order of magnitude smaller than a single large cyclone. This also benefits assembly weight and fluidic assembly volume. Further, the use of micro-machined, parallel components allows the particle separation and collection system to be assembled into smaller or larger architectures, making it extremely flexible and adaptable for a wide range of possible applications that can be integrated with a number of different biosensor or other detector technologies.